EPHEMERIDuE. 



595 



two abdominal setae, while the four wings are provided with 

 numerous cross-veins. The eyes are simple, and in the males 

 of large size and placed very near each other. Baetis inter- 

 punctata Say is a yellowish white species tinged with green, 

 with an arcuate black line on the front, and a lateral black 

 point, while the prothorax has one black stripe on the side. 



The singular genus Bwtisca is very thick-bodied, and differs 

 from the other Ephemerids in the fifth abdominal joints being 

 twice as long as any of the others. 

 The pupa (Fig. 576, i ; a, lateral 

 tooth ; n, antenna ; in, section of 

 the abdomen, the numerals indicat- 

 ing the segments ; a, branchiae, 

 above which is a flap, b) "differs," 

 according to Walsh, "from all de- 

 scribed Ephemerinous pupae in the 

 antennae being eight-jointed or there- 

 abouts, not multiarticulate, and also 

 in the branchiae being internal and 

 not used for locomotive purposes, 



and from all larvae and pupae, and indeed from all known 

 hexapod insects in any of their states, in the pro-, meso- and 

 metanotum being connate and confluent, and extending over 

 one-half of the abdomen in the form of a large, dilated, convex 

 carapace, or shield, thus giving the in- 

 sect a very Crustacean appearance." 

 The larva, early in its life, has rudi- 

 mentary wings, as in many grasshoppers, 

 but in the pupa state they are not 

 present. 



Near Baetis comes Potamanthus ^ which 

 has three caudal setae and four wings 



O 



provided with numerous cross- veins ; the 

 eyes in the males are double, large and Fi s- 577. 



approximate. The Potamanthus cupidus of Say is black, with 

 a broad dorsal stripe and a lateral impressed line on each side 

 of the thorax. P. marginatus Zetterstedt (Fig. 577), a boreal 

 European species, we have found in abundance in Labrador fly- 

 ing over pools in July. 



